Figure 1.

Resealing modes of the permeability barrier. Cartoons sketch conceivable behaviours of the barrier towards nuclear transport receptors (NTRs) and inert material. (A) A scenario in which NTRs can penetrate into and through the barrier, but where no resealing behind the translocating species occurs. In this case, NTRs would cause a breakdown of the barrier. The problem should occur already at low NTR concentrations and would worsen with time. Eventually, the gel would disintegrate. (B) A scenario where resealing behind the translocating species is slow. In this case, NTRs would transiently collapse the barrier. The problem would increase with the load of facilitated gel entry. (C) A scenario where the barrier reseals immediately behind a translocating species. In this case, the barrier would stay tight against inert material, even at the highest transport load.